package module import ( "encoding/xml" "fmt" "io" "net/http" "net/url" "strings" ) // HttpGetter is a Getter implementation that will download a module from // an HTTP endpoint. The protocol for downloading a module from an HTTP // endpoing is as follows: // // An HTTP GET request is made to the URL with the additional GET parameter // "terraform-get=1". This lets you handle that scenario specially if you // wish. The response must be a 2xx. // // First, a header is looked for "X-Terraform-Get" which should contain // a source URL to download. // // If the header is not present, then a meta tag is searched for named // "terraform-get" and the content should be a source URL. // // The source URL, whether from the header or meta tag, must be a fully // formed URL. The shorthand syntax of "github.com/foo/bar" or relative // paths are not allowed. type HttpGetter struct{} func (g *HttpGetter) Get(dst string, u *url.URL) error { // Copy the URL so we can modify it var newU url.URL = *u u = &newU // Add terraform-get to the parameter. q := u.Query() q.Add("terraform-get", "1") u.RawQuery = q.Encode() // Get the URL resp, err := http.Get(u.String()) if err != nil { return err } defer resp.Body.Close() if resp.StatusCode < 200 || resp.StatusCode >= 300 { return fmt.Errorf("bad response code: %d", resp.StatusCode) } // Extract the source URL var source string if v := resp.Header.Get("X-Terraform-Get"); v != "" { source = v } else { source, err = g.parseMeta(resp.Body) if err != nil { return err } } if source == "" { return fmt.Errorf("no source URL was returned") } // Get it! return Get(dst, source) } // parseMeta looks for the first meta tag in the given reader that // will give us the source URL. func (g *HttpGetter) parseMeta(r io.Reader) (string, error) { d := xml.NewDecoder(r) d.CharsetReader = charsetReader d.Strict = false var err error var t xml.Token for { t, err = d.Token() if err != nil { if err == io.EOF { err = nil } return "", err } if e, ok := t.(xml.StartElement); ok && strings.EqualFold(e.Name.Local, "body") { return "", nil } if e, ok := t.(xml.EndElement); ok && strings.EqualFold(e.Name.Local, "head") { return "", nil } e, ok := t.(xml.StartElement) if !ok || !strings.EqualFold(e.Name.Local, "meta") { continue } if attrValue(e.Attr, "name") != "terraform-get" { continue } if f := attrValue(e.Attr, "content"); f != "" { return f, nil } } } // attrValue returns the attribute value for the case-insensitive key // `name', or the empty string if nothing is found. func attrValue(attrs []xml.Attr, name string) string { for _, a := range attrs { if strings.EqualFold(a.Name.Local, name) { return a.Value } } return "" } // charsetReader returns a reader for the given charset. Currently // it only supports UTF-8 and ASCII. Otherwise, it returns a meaningful // error which is printed by go get, so the user can find why the package // wasn't downloaded if the encoding is not supported. Note that, in // order to reduce potential errors, ASCII is treated as UTF-8 (i.e. characters // greater than 0x7f are not rejected). func charsetReader(charset string, input io.Reader) (io.Reader, error) { switch strings.ToLower(charset) { case "ascii": return input, nil default: return nil, fmt.Errorf("can't decode XML document using charset %q", charset) } }